Poa annua L., Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 26 (Go to the risk assessment).

Common name(s): [more details]

Chinese: zao shu he

English: annual bluegrass, annual meadowgrass, annual poa, annual wintergrass, goose grass, walkgrass, winter grass

French: pâturin annuel

Japanese: suzumeno-katabira

Spanish: cebadilla, champa, espiguilla, hierba de la perdiz, hierba de punta, pastito de invierno, pasto azul anual, pasto de la perdiz, pasto de las liendres, pata de gallina, pata de perdiz, pel de ca, pelosa, piagillo, piojillo, poa annual, zacate azul, zacate poa

Habit:  grass

Description:  "Bright green annuals; culms spreading or sometimes erect, rooting at modes and forming mats, 0.3-2 (-3.5) dm tall, strongly flattened.  Sheaths open ca. 1/2 their length, with overlapping margins; ligule 1-3 mm long, obtuse or truncate, often erose; blades lax, folded or flat, 1-10 cm long, 1-2.5 (-3) mm wide, margins scaberulous, otherwise glabrous.  Panicles open, pyramidal, 1.5-3.5 (-8) cm long, branches spreading, usually rigid; spikelets 3-6-flowered, (3-) 4-5.5 (-7) mm long, rachilla elongate; glumes glabrous, first glume narrowly lanceolate, 1.5-2.2 mm long, 1-nerved, apex acute, second glume oblanceolate to obovate, slightly longer than first glume, 1.8-2.7 mm long, 1-3-nerved, somewhat obtuse; lemmas 2.5-3.5 mm long, prominently 5-nerved, the nerves villous toward base, the margins scarious toward apex, pilose toward base; palea 1.5-2 mm long, 2-nerved, keeled, nerves villous, margins hyaline.  Caryopsis pale brown, ellipsoid, somewhat trigonal, ca. 1 mm long"  (Wagner et al., 1999; p. 1583).

Description from GrassBase.

Habitat/ecology:  "It invades gardens, lawns, foot paths, bowling greens, flower beds, golf courses, and cracks in sidewalks and pavement.  It can be found at the margins of ponds and streams as well as in agronomic and horticultural crops and pastures.  It occurs in areas of 90 to 430 mm annual precipitation; average minimum and maximum temperatures of 4.9 and 27.4° C, respectively; and soil pHs from 4.5 to 8.2.  It grows on a wide range of soils, tolerates trampling, and is a frequent weed in areas heavily trafficked by livestock or humans"  (Holm et al.,  1997; p. 587).  In Hawai‘i, "naturalized and relatively common, occurring in a variety of disturbed, usually mesic habitats, including roadsides, pastures, urban sites, and disturbed mesic and wet forest, 0-1,830 m" (Wagner et al., 1999; p. 1583).

Propagation:  Seed

Native range:  Europe (Wagner et al., 1999; p. 1583).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Pacific offshore islands) Lord Howe Island	Lord Howe Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 23) "An introduced and now common weed, especially of cultivated ground, including lawns". Vouchers cited: A.C. Beauglehole 5423 (CANB, MEL), A.N. Rodd 1480 (K, NSW), L.M. Bingley 11 (K), J.C. Game 69/273e (K)
Australia (Pacific offshore islands) Norfolk Islands	Norfolk Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 12) "An introduced and now common weed, especially of cultivated ground, including lawns". Voucher cited: R.D. Hoogland 11233 (CANB)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced	Skottsberg, Carl (1953) (p. 215)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 556)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced	Skottsberg, Carl (1953) (p. 215)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 556)
Ecuador (Galápagos Islands) Isabela Group	Isabela Island	introduced cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Isabela Group	Volcán Sierra Negra, Isabela Island	introduced invasive	Charles Darwin Foundation (2008)
French Polynesia Society Islands	Tahiti Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2011) Adventice
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
State of Hawaii Hawaiian Islands	Kure Atoll	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
State of Hawaii Hawaiian Islands	Kure Atoll	introduced invasive	Starr, Forest/Martz, Kim/Loope, Lloyd (2001) (p. 16) Uncommon. Only found around quarters.
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Starr, Forest/Starr, Kim (2011) (p. 33) East Maui. Voucher cited: Starr & Starr 090504-03 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
Japan (offshore islands) Bonin (Ogasawara) Islands	Bonin (Ogasawara) Islands		Kato, Hidetoshi (2007)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced	MacKee, H. S. (1994) (p. 61) Voucher cited: Cribs 847
New Zealand (offshore islands) Kermadec Islands	Kermadec Islands	introduced invasive	Edgar, E./Connor, H. (2000) (p. 141) "A weed of cultivated land and waste places".
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)	introduced cultivated	Henty, E. E. (1969) (p. 154)
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Philippines Philippine Islands	Philippine Islands	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
United States (other Pacific offshore islands) Midway Atoll	Midway Atoll	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1583)
United States (other Pacific offshore islands) Midway Atoll	Sand Island	introduced invasive	Starr, Forest/Starr, Kim/Loope, Lloyd (2008) (pp. B-12)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	New South Wales	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Australia Australia (continental)	Northern Territory	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Australia Australia (continental)	Queensland	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Chile (continental) Chile	Chile (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
China China	China (People's Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
China China	Hong Kong	native	Wu, Te-lin (2001) (p. 344)
Colombia Colombia	Colombia (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Costa Rica Costa Rica	Costa Rica (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 285)
Ecuador (Mainland) Ecuador	Ecuador (Republic of) (continental)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
El Salvador El Salvador	El Salvador (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 285)
Honduras Honduras	Honduras (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 593)
Indonesia Indonesia	Indonesia (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Japan Japan	Japan (country)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 192)
South Korea South Korea	South Korea (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Malaysia Malaysia	Malaysia (country of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Mexico Mexico	Mexico (United Mexican States)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Edgar, E./Connor, H. (2000) (p. 141) "A weed of cultivated land and waste places".
Nicaragua Nicaragua	Nicaragua (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 593)
Perú Perú	Perú (Republic of)	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)
Taiwan Taiwan	Taiwan Island	introduced invasive	Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 585)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Comité français de l'Union Internationale pour la Conservation de la Nature en France (2010) Envahissant principalement dans les milieux perturbés.
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 285)

Additional information:
Photos and description at University of California Integrated Pest Management Program

Additional online information about Poa annua is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Poa annua as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Poa annua may be available from the Germplasm Resources Information Network (GRIN).

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Charles Darwin Foundation. 2008. Database inventory of introduced plant species in the rural and urban zones of Galapagos. Charles Darwin Foundation, Galapagos, Ecuador.

Comité français de l'Union Internationale pour la Conservation de la Nature en France. 2010. Les espéces envahissantes en outre-mer (online resource).

Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido. 2006. Nouveau catalogue de la flore vaculaire de l'archipel Juan Fernández (Chile) [Nuevo catálogo de la flora vacular del Archipélago Juan Fernández (Chile)]. Acta Bot. Gallica 153(4):399-587.

Edgar, E./Connor, H. 2000. Flora of New Zealand, vol. V: Gramineae. Manaaki Whenua Press. .

Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. 2011. Base de données botaniques Nadeaud de l'Herbier de la Polynésie Française (PAP). (online resource).

Hafliger, Ernst/Scholz, Hildemar. 1980. Grass weeds, vol. 2. CIBA-GEIGY Ltd., Basle, Switzerland. 137 pp. + plates.

Henty, E. E. 1969. A manual of the grasses of New Guinea. Department of Forests, Division of Botany, Botany Bull. No. 1. Lae, New Guinea. 215 pp.

Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James. 1997. World weeds: natural histories and distribution. John Wiley & Sons. 1129 pp.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

Kato, Hidetoshi. 2007. Herbarium records of Makino Herbarium, Tokyo Metropolitan University. Personal communication.

MacKee, H. S. 1994. Catalogue des plantes introduites et cultivées en Nouvelle-Calédonie. Muséum National d'Histoire Naturelle, Paris, 164 p.

Merrill, Elmer D. 1925. An enumeration of Philippine flowering plants, vol. 1 [reprint]. Bureau of Printing, Manila. 463 pp.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

Orchard, Anthony E., ed. 1994. Flora of Australia. Vol. 49, Oceanic islands 1. Australian Government Publishing Service, Canberra.

Skottsberg, Carl. 1953. The natural history of Juan Fernandez and Easter Island. Vol. II, Botany. Almqvist &l; Wiksells, Uppsala. 960 pp.

Starr, Forest/Martz, Kim/Loope, Lloyd. 2001. Botanical inventory of Kure Atoll. United States Geological Survey, Biological Resources Division, Haleakala Field Station, Hawai‘i. 22 pp.

Starr, Forest/Starr, Kim. 2011. New plant records from midway Atoll, Maui and Kaho‘olawe. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2009-2010. Part II: Plants. Bishop Museum Occasional Papers. 110:23-35.

Starr, Forest/Starr, Kim/Loope, Lloyd. 2008. Botanical survey of Midway Atoll. Prepared for: United States Fish and Wildlife Service. 27 pp. plus appendices.

U. S. Government. 2011. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Wu, Te-lin. 2001. Check List of Hong Kong Plants. Hong Kong Herbarium and the South China Institute of Botany. Agriculture, Fisheries and Conservation Department Bulletin 1 (revised). 384 pp.

Zhengyi, Wu/Raven, Peter H./Deyuan, Hong. 2011. Flora of China (online resource).